A True Desert Rose — Purshia stansburyana

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Stansbury’s Cliff-Rose (Purshia stansburyana) spotted at park headquarters at Petrified Forest National Park in Arizona. This scrappy-looking plant puts forth fragrant and attractive blooms from April to June.  Image credit: Curious Sengi.

A sweet fragrance drifts in the hot afternoon air.  The scent comes from pale yellow flowers set against tough, stubby evergreen leaves.

This is Stansbury’s Cliff-Rose (Purshia stansburyana), a true rose in the family Rosaceae and a common native plant through the desert lands of Arizona, Utah, Colorado, New Mexico, Nevada, southern California, and northern Mexico.  This plant grows as a shrub or small tree, usually 1 – 6 feet (0.3 – 1.8 m) tall.  Reports of plants nearly 70 years old have been made, but they are more likely to live up to 40 years.  During the long life of Stansbury’s Cliff-Rose, it provides an important source of browse for domestic cattle and sheep, as well as mule deer, elk, pronghorn, desert bighorn sheep, and many bird species.  Rodents feed on the seeds.  Native peoples have made good use of the plant as well:  the inner bark was made into ropes, clothing, sandals, and baskets; the wood was rendered into arrow shafts; and the leaves were medicinally used as both an emetic and a wound wash.  Modern pharmaceutical studies seem to indicate that triterpenoids extracted from the plant might have some inhibitory effects on viruses such as HIV and Epstein-Barr (which causes mono and is associated with specific forms of cancer).

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As the flowers fertilize and come into fruit, long feathery plumes erupt from the center.  They are derived from female portions of the flower, called the style, which persist as these remarkable extensions up to 2 inches in length.  These plumes can catch the wind or hitch a ride with passing animals to help disperse the seeds.  Image credit: Curious Sengi.

Members of the genus Purshia form a large species complex capable of easy cross-fertilization and hybridization.  This tendency towards hybridization has raised some conservation concerns that the ubiquitous P. stansburyana will swamp out rarer speciesespecially with the breakdown of natural ecological barriers through climate change and road construction.  Despite these concerns, Stansbury’s Cliff-Rose continues to define the landscape of the high desert cliffs and rocky hillsides, providing food and shelter for wildlife and fixing nitrogen in the soil.  The plant is recommended for seeding in areas in need of habitat restoration from disruptive human activities such as mining.

Howard Stansbury

Howard Stansbury.  Image credit: Tiehm 1987.

P. stansburyana was named for Captain Howard Stansbury (1806 – 1863) of the Corps of Topographical Engineers of the U.S. Army, who led a surveying expedition to the Great Salt Lake in 1849 – 1850.  His party brought back specimens that were later described and named by New York botanist John Torrey (1796 – 1873).  In handing over the collected plants, Stansbury had to make apologies to Torrey due to the sudden disappearence of the expedition’s naturalist, who “. . . .being violently attacked with the California fever, unceremoniously abandoned his post and walked off to the mines, leaving me to shift for myself.  Consequently the collection was made by persons but little acquainted with botany, and I fear you will not find it of any great value (quoted from Tiehm 1987).”  Stansbury seems to have lost a number of men to the new California gold rush, but the expedition was a major success and Stansbury remains honored in the name of this lovely desert rose.

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This charming native plant is becoming increasingly popular as a drought-resistant ornamental plant for gardens.  Image credit: Curious Sengi.

 

References

Baggs, Joanne E. & J. Maschinski.  2000.  “The Threat of Increasing Hybridization of an Endangered Plant Species, Purshia subintegrata, in the Verde Valley, Arizona.”  Southwestern Rare and Endangered Plants:  Proceedings of the Third Conference.  PP. 25 – 28.

Howard, Janet L.  1995.  “Purshia mexicana var. stansburiana.”  Fire Effects Information System.  U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Library.  Accessed 29 June 2016.

Pendleton, R.L. & E.D. McArthur.  1995.  “Reproductive Biology of Bitterbrush:  Interaccessional Hybridization of Plants Grown in a Common Garden.”  Proceedings — Ecology and management of annual rangelands. General Technical Report INT-GTR-313, USDA Forest Service, Intermountain Research Station, Ogden, UT.  Pp. 266 – 270.

Stubbendieck, James, Stephan L. Hatch, & L.M. Landholt.  2003.  North American Wildland Plants:  A Field Guide.  Lincoln, NE:  University of Nebraska Press.

Tiehm, Arnold.  1987.  “Index to Plants Collected on Howard Stansbury’s Expedition to the Great Salt Lake, 1849 – 1850.”  Brittonia 39 (1):  86 – 95.

 

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Flowering of the Dogwood

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Image credit: Curious Sengi.

Blooming of the dogwood trees is a portentious sign that spring, at long last, is finally here to stay.

The tetrad of creamy white or pink-petaled flowers are not actually flowers at all, but specialized leaves called bracts.  Bracts are usually found as associated supports to flowers and other reproductive structures.  The true flowers are at the center of this arrangement and unfurl as a cluster of tiny yellow blossoms.  In the early autumn, these clusters transform into bright red drupe fruit.

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Image credit: Curious Sengi.

Within the United States, you are most likely to see a cultivar of Cornus florida.  This popular ornamental tree has a native distribution throughout the eastern part of the country from Maine to Florida.  Dogwoods are shade-tolerant denizens of the understory that grow interspersed with other trees forming the canopy above them.  Despite this modest standing, dogwoods are an important component of the local ecosystem.  Their leaves decompose rapidly, releasing mineral nutrients and improving the neighboring soil.  Dogwood fruits, flowers, leaves, and bark are all particularly rich in calcium and fat for the animals that feed on them.  The fruit alone are known to feed over 30 bird species and many mammals.  The wood is hard and smooth-grained, making it desireable as a fine craft wood and for making tool parts subject to heavy usage.

Cedar Waxwing (Bombycilla cedrorum) enjoying some fruit of the Flowering Dogwood (Cornus florida). Image credit: Gypsy Flores via Birds & Blooms.

Cedar Waxwing (Bombycilla cedrorum) enjoying some fruit of the Flowering Dogwood (Cornus florida). Image credit: Gypsy Flores via Birds & Blooms.

The evolutionary history of the whole dogwood clade was a biogeographical mystery, an unknown saga of worldwide meanderings now reconstructed from molecular, morphological, and fossil data.  There are about 58 species in the genus Cornus today and they are distributed in temperate and subtropical regions of North America, Europe, Africa, East Asia, and a sole species outposted in South America.  Earlier studies had suggested an Asian origin for dogwoods, but a recent study incorporating fossil material point towards a European birthplace.  Dogwoods arose in Europe during the Early Paleocene or Late Cretaceous, around 65 million years ago, and within a span of about 10 to 20 million years, the trees made multiple trans-Atlantic dispersals to North America.  The lone South American species was a result of migration from original colonizations in the north.  Though Europe and North America were much closer together during the Paleocene, when the young Atlantic ocean had yet to push the two continents away as distant as they are now, the exact mechanism of how dogwoods could travel over the salt waters has yet to be explained.

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Image credit: Curious Sengi.

 

References

McLemore, B.F.  1990.  “Cornus florida L.  Flowering Dogwood.”  In Silvics of North America:  Volume 2, Hardwoods.  United States Department of Agriculture.  Pp. 278 – 283.

Xiang, Q.-Y. et al.  2006.  “Species level phylogeny of the genus Cornus (Cornaceae) based on molecular and morphological evidence — implications for taxonomy and Tertiary intercontinental migration.”  Taxon 55 (1):  9 – 30.